Human blood is routinely collected in sealed, evacuated test tubes and centrifuged to separate the lighter serum or plasma portion from the heavier red blood cells. Typically a portion of the serum or plasma is then removed and tested. Today, much of the removal and testing is done by machines. While the separated blood is stored awaiting testing certain chemicals can migrate between the separated layers giving incorrect test results. Consequently, the art has developed a variety of separators having a specific gravity between the serum or plasma and the red blood cells. These separators are either solid devices or gels.
The first evacuated separator tube was sold by Becton Dickinson under the trademark Vacutainer®, invented by Joseph Kleiner in 1950. The next significant development is disclosed in my U.S. Pat. No. 3,508,653 licensed to Corning for a gel separator. But neither Becton Dickinson nor Corning could develop a functional evacuated solid separator tube for use with a blood specimen.
The critical failing in the attempt to develop a blood collection tube with solid separator was the inability to form and maintain a robust seal because maintaining glass tube's dimensions during the manufacturing process was virtually impossible. Greiner's introduction of molded barrier polyethylene terephthalate [PET] enabled matching of precision molded separator floats disclosed in my U.S. Pat. No. 5,736,033. The patent contains a review of the pertinent prior art up to April 1998.
In my U.S. Pat. No. 5,065,768 I disclose tubes with self-sealing plugs having an air vent channel which automatically seals a few seconds after the blood sample contacts the plug. The blood sample may then be dispensed with aid of a special pipette, or centrifuged in a microhematocrit or functionally similar centrifuge at about 11,000 g after collection of the fluid. This provides a packed cell volume reading, which may be followed by plasma dispensation from that tube. This invention is directed primarily toward the collection of blood from finger sticks, and discloses self-sealing plugs that seal off the air vent as a direct result of contact with the specimen at the time the sample is filled with blood from skin punctures. This invention does not relate to sealing devices that are intended to begin to seal during and after centrifugation has begun. Furthermore, the patent teaches that solid separators or gels are used to separate the phases of centrifuged blood.
My U.S. Pat. No. 5,736,033 discloses a solid separator which seals the separated blood phases in a blood collection tube. This device has a separator that has a specific gravity between the light and heavy phases of the blood, preferably between 1.03 and 1.06. The separator has a peripheral water swellable band generally flush and recessed within a molded body. The specific gravity of the separator is determined primarily by the specific gravity of the body, and to a lesser amount by the water swellable band. The body is a molded plastic material that may contain other material. For example, a magnetic separator can be constructed from a combination of a molded polypropylene component and iron or steel elements such that the separator has a specific gravity between 1.03 and 1.06.
The extensive use of high throughput analyzers and strong interest in biomarkers for the molecular diagnosis of disease has created a need for a simple, effective, and economical solid device for separation of plasma. This separator must have an overall density that assures the separator will always be positioned correctly for the formation of buffy coat rings used for genetic, microbiological, and other testing purposes as well as to aid collection of platelets used in coagulation studies such a separator should be formulated to have an overall specific gravity within a limited range. This makes the separator especially useful for automatic sampling machines and enables the rapid collection of specific cells of interest, particularly cells of the buffy coat and cells that have been marked with immuno-fluorescent dots, nanoparticles of various types, confocal, and confocal hyphenated systems, and various other tags. There is also a need for a solid separator to facilitate the harvesting of lymphocytes and monocytes in contemporary clinical laboratory testing for a multitude of immunological, genetic, microbiological, and other testing purposes as well as to aid collection of platelets and small white cells used in coagulation studies. Such a separator should be formulated to have an overall specific gravity within a limited range.
Contemporary cutting edge laboratories have an urgent need to reduce costs, and yet be able to analyze a diversity of blood specimens for a variety of tests. Hospital centers such as the University of Pittsburgh Medical Center, with their set of 24 affiliated hospitals and 4 core laboratories are now running millions of tests daily. Hospitals and laboratories that conduct tests on centrifuged blood such as ARUP Laboratories, one of the most advanced laboratories, have an immediate urgent need for a separator that can be used in blood collection tubes that are centrifuged such that after separation the buffy coat or other cells of interest will be at a known position in the tube and can be extracted with automated testing equipment. This separator must travel through the blood during centrifuging in a manner so that cells are not damaged. Finally, the separator must maintain a seal between the separated blood phases.